Dry, granular adsorbent materials are used for a variety of industrial and household purposes, including oil absorption. Nonetheless, the absorption and removal of oil often creates environmental issues. In fact, many authorities have banned the flushing of environmentally hazardous oil residues into storm drain systems which flow into our natural ecosystems. Even when contaminated residues collected from and combined with cleaning materials are discarded into solid waste dump sites, they represent eco-hazards by having their soluble, ionizing contaminants as well as non-soluble, unbound oil and chemical contaminates bleed and leach into the soil and groundwater.
U.S. Published Patent Application No. US2006/0276361A1 refers to surface cleaning and contaminant absorption compositions. While these complex compositions appear friendlier to the environment than other compositions in the art, they contain Zeolite® (chemically known as potassium-calcium-sodium aluminosilicate), fly ash, carbonates, charcoal, and/or surfactants. The surfactants are described as an active agent to aid absorption, i.e., by increasing the wetting and emulsifying capacity of the compositions. The negative aspect of these surfactants is that they aid the contaminant to leach out when disposed of and thus is not eco-compatible. The concrete asphalt cleaning art described in this application also mentions a solvent, preferably diproplylene glycol monomethyl, to dissolve surface contaminants. These solvents also aid the bleeding/leaching of contaminants into the soils of the solid waste site and become contaminants themselves.
Other prior art cites various adsorbents, absorbents and cleaning materials. The disadvantage of these compositions is that they produce complex contaminated residues unsuitable for disposal in sanitary/storm drains.
For example, Cervero's U.S. Pat. No. 6,827,792 B2 discloses the creation of admixtures of inorganic salts with silica gel (amorphous silica) to absorb liquid wastes, oils and hydrocarbons. Similarly, WO/2007/104955 describes carpet cleaning compositions that contain at least 30% of precipitated or fumed silica component (also amorphous silica), with preferential amounts greater than 50% by weight, to which is added alkali metal salts and an active detergent. Dozens of types of detergents are listed including eco-harmful phosphates which are discouraged or banned in most states. The use of ionizing salts in these formulations causes high solubility and thereby detracts from the ability of the amorphous silica to absorb liquid wastes, oils and hydrocarbons. Moreover, the ionizing salts can cause any liquid wastes, oils and hydrocarbons absorbed by the amorphous silica to bleed and leach away when placed in waste dumps.
U.S. Pat. No. 5,951,784 teaches scrubbing with detergent, phosphates and other surfactants to clean oil off concrete followed by rinsing with water and subsequently, in a second application, introduction of a fine clay absorbent to remove the stain. This is onerous and results in unacceptable contaminated waste, unfit for disposal.
U.S. Pat. No. 5,723,424 pertains to a concrete cleaning mixture described as two components. The first component consists of a granular Oil-Dri® type absorbent attapulgite clay material combined with granular cat litter/attapulgite-type clay. This is rubbed onto the oil contamination and then removed. The second component consists of kaolin-type clay and finely ground clay dust that absorbs the oil from pores and crevices. Use of this product is laborious and produces unbound contaminated waste that easily allows oil to bleed/leach when disposed of in landfill.
U.S. Pat. No. 7,041,221 B2 uses crushed glass as an absorber of oil from surface water whereby the crushed glass sinks when it is coated with oil and is subsequently recovered, then recycled into roof shingles or asphalt. The disclosed recycling acknowledges the eco-threat of the contaminated absorbate, which cannot be discarded into solid waste dump sites because the oil will bleed into the soil since the oil is not permanently bound to the crushed glass. The same is true if this method had been used to remove oil from a solid surface.
U.S. Published Patent Application No. US2005/0028839 A1 teaches a method for treating spills on roadways by using biodegradable absorbent material consisting of peat moss and coconut coir to absorb and remove spills. U.S. Pat. No. 6,391,120 B1 describes use of coconut coir pith as sorbent. U.S. Pat. No. 4,670,156 discloses use of hydrophobic sorbent, particularly expanded reject fibers that absorb even heavy oils. U.S. Pat. No. 5,244,503 uses polyvinyl acetal to bind to absorbate and confirms “the adsorbent laden with absorbate should here arise in the most particulate or compacted form possible without adhering liquid oil residues, so that it can be collected mechanically and passed to disposal.” All sorts of synthetics and other diverse oil sorbents such as polypropylene plastic foams, matting, and mixtures of fibers can absorb oil from water surfaces. They unfortunately all have the disadvantage of leaching liquid oil residues.
Numerous methods for removal of oil spills are well known and established in the art. The U.S. Environmental Protection Agency (EPA), for example, outlines response techniques at their website www.epa.gov/oilspill/oiltech.htm Use of natural and synthetic sorbent materials are described including advantages and disadvantages.
There is a great need for oil and oil stain removal that is done with materials that are totally compatible with the environment, easy to produce, easy to remove and, when discarded, does not bleed or leach back into the environment.